MUNICH (AP) — NATO's secretary general said Saturday the alliance has no intention of backing down on its plans for a European missile defense system, despite ongoing criticism from Russia.

Anders Fogh Rasmussen told a small group of reporters on the sidelines of the Munich Security Conference that in dealings with Moscow "this question of missile defense remains ... the big elephant in the room." But he said NATO's decision has been made and he hopes Russia will work together with the alliance on the issue.

"We have made clear from the outset that NATO has made the decision to establish a NATO missile defense system because it's our obligation to ensure effective defense of our populations," Fogh Rasmussen said. "Having said that, we have invited Russia to cooperate and ... now it's up to Russia to engage in that."

The comments came after Russian Foreign Minister Sergey Lavrov told the gathering of top diplomats and defense officials that NATO's missile defense program and eastward expansion have caused undue friction reminiscent of the Cold War.

"Officially we have abandoned the mindset of the Cold War — Russia and NATO countries say that they do not see each other as adversaries ... but we should admit that we should still come a long way to match our words with deeds," Lavrov said.

The U.S. and NATO say the missile defense plan is aimed at fending off an Iranian missile threat, but Moscow has rejected the claim, saying the system may eventually grow powerful enough to threaten Russia's nuclear deterrent.

U.S. Vice President Joe Biden's office said he met with Lavrov later behind closed doors and "emphasized the importance of the two countries working together in the interest of international peace and security."

During the conference, Fogh Rasmussen urged cash-strapped European nations not to use the alliance's drawdown of forces in Afghanistan as an excuse to cut defense spending.

"We must build on what we have gained in operations such as Afghanistan, not cash in on what some may perceive as the post-ISAF dividend," he said.

"In this age of austerity, that looks like an attractive option, but it would be the wrong option. Because security challenges won't wait while we fix our finances, and more cuts now will lead to greater insecurity in the future, at a cost we simply can't afford. We saw this after the Cold War, when we were ill prepared to respond to the crises in the Balkans."

He noted that since 2001, the U.S. share of NATO defense spending has risen from 63 percent to 72 percent, while most European nations have cut their defense budgets.

U.S. Deputy Defense Secretary Ashton Carter noted that U.S. officials speaking at the conference have in the past often exhorted allies to "provide the necessary resources for defense."

"This time ... I have to add my own country to this exhortation," he said, pointing to the prospect of across-the-board cuts as politicians in Washington wrangle over the budget.

Carter said there is "the very real prospect of huge and reckless additional cuts of a size and magnitude and manner that I, as the Department of Defense's chief management officer, cannot tell the president will do anything other than devastating damage to the military."

"It can be avoided and it can be reversed," he said. "In that regard I used to be hopeful and optimistic, and now I'm just hopeful."

Fogh Rasmussen said that, instead of cuts, European NATO countries should use funds saved from the Afghanistan drawdown to invest in capabilities where they have found themselves lacking.

"We have learned lessons from our operations in Afghanistan as well as Libya and Mali," where the alliance isn't operating but some of its members are. "What we see is that ... such operations couldn't be carried out successfully without a significant American contribution," he said.

"It is necessary for Europe to invest more in long-distance airlift capacity, in air-to-air refueling as we learned in Libya, in intelligence, surveillance, reconnaissance capabilities — in all these areas."